1. Field of the Invention
The present invention generally relates to an end-point detecting method and the related manufacturing apparatus. More specifically, the present invention relates to a method using frequency modulation to determine the end-point of the manufacturing process and the related manufacturing apparatus.
2. Description of the Related Art
In the semiconductor manufacturing process, the end-point method is used to control the manufacturing time, which influences the quality of the product. FIG. 1 is a conventional manufacturing apparatus. The manufacturing apparatus 10 comprises a manufacturing device 12, a control device 14 and an end-point detecting device 16. The desired manufacturing process is performed in the manufacturing device 12 and a process signal PS is provided. The control device 12 provides the control signal CS controlling the power supply needed by the manufacturing device 12 and the enabling mechanism of the manufacturing device 12. During the manufacturing process, the end-point detecting device 16 monitors the manufacturing signal and determines whether the manufacturing device 12 is operating within predetermined conditions. An end-point is determined when the end-point detecting device 16 detects the manufacturing device 12 is operating outside the predetermined conditions. At this time, the end-point detecting device 16 informs the control device 14 to carry out a reaction to stop the manufacturing process or change the manufacturing parameter to begin the next manufacturing step.
For the purpose of illustration, assume the manufacturing apparatus 10 is a plasma etching system, the manufacturing device 12 could be a vacuum chamber, the control device 14 could be a power supply for providing a RF plasma power source or a general power supply to the vacuum chamber. In this case, the end-point detecting device 166 detects the light intensity signal generated by discharge of electrons of the plasma in the vacuum chamber and determines the plasma etching state in the vacuum chamber.
Generally, the end-point detecting method is used only after the manufacturing process has continued for a predetermined time and a stable state has been obtained. Thus, the misjudgment of the end-point caused by the unstable state of at the beginning of the manufacturing process can be avoided.
Most conventional end-point detecting methods simply monitor the process signal PS generated by the manufacturing device 12. One end-point detecting method averages the process signals collected over a time period after the procedure is started as the standard average value. The standard average value is compared to the current process signal PS to determine whether an end-point is reached. Referring to FIG. 2, the process signals PS from 0 to time Ta are averaged to obtain a standard average value Ia. If the current process signal is less than 0.9Ia, an end-point is detected.
However, accidental noises might affect the state of the manufacturing device 12. For example, a bad ground connection or aged components in the control device 14 might cause the power supply to the manufacturing device 12 to have a sudden power surge. The end-point detecting device 16 could incorrectly take the instance of the power surge as the end-point and mistakenly stop the manufacturing process.
A time-average method can be used to overcome the problem of an unstable end-point. For the best time-average result, a long period is used to do signal averaging. In other words, the sudden noise is xe2x80x9cdilutedxe2x80x9d by a long period, so that the judgement of the end-point won""t be affect. However, in real processes, this is impractical, as the manufacturing process will be delayed.
Therefore, an object of the present invention is to provide an end-point detecting method using frequency modulation to accurately find the end-point of the manufacturing process in a manufacturing device.
The present invention provides a method of frequency modulated end-point detection. First, control signals are sent to the manufacture device for performing the manufacturing process, wherein process signals are generated along with the manufacturing process. Then, the process signals are filtered to obtain synchronization signals synchronized with the control signals. Then, a judging standard is provided according to the synchronization signals corresponding to a specific state of the process. Finally, the synchronization signals are continuously monitored, and a process end-point is determined when the synchronization signals do not meet the judging standard.
The present invention further provides a manufacturing system with method of frequency modulated end-point detection. The manufacturing system has a control device, a manufacturing device and an end-point detecting device. The control device provides control signals. The manufacturing device performs a manufacturing process controlled by the control signals and generates process signals. The end-point detecting device monitors and filters the process signals to generate synchronization signals synchronized with the control signals. Furthermore, the end-point detecting device determines an end-point according to a judging standard defining the value of the synchronization signals corresponding to a specific state of the process.
The advantage of the present invention is the filtering of external noises. Because the external noises always have a different frequency than that of the control signals, the judging standard may eliminate the effect of the external noises and the end-point is thus found is accurately. Even though the control signals could be distorted slightly by the external noises, the effect can be countered by applying a simple computation of the ratio between the synchronization signal and the control signals.